The present invention relates to a pipe coupling and particularly to a valve used in a pipe coupling.
FIG. 1 shows one example of a male coupling member provided with a conventional valve 10.
The valve 10 consists of a valve body 12 and a valve seat 20 formed on the wall surface toward the inside of the end opening 18 of the fluid passage 16 of the coupling member 14.
The valve seat 20 is formed from a conical wall surface 21 wherein the wall surface of the fluid passage 16, which is cylindrical overall, is conical with its apex pointed toward the end opening 18. The valve body 12 consists of a shaft 22, a disk-shaped sealing ring support 24 formed at the tip of the shaft 22, a sealing ring 26 supported by the support 24, and a valve head 28 that sandwiches the sealing ring 26 against the sealing ring support 24. The valve head 28 consists of a conical part 30 adjacent to the sealing ring 26, and a protruding part 32 that extends forward from the front-end surface of the conical part 30.
When the valve body 12 is in the closed position shown in FIG. 1 so as to close the fluid passage 16, the valve body 12 is pressed against the valve seat 20 by means of a coil spring 36 mounted between the valve body 12 and a spring support 34 secured to the inner wall surface of the fluid passage 16. The conical part 30 of the valve head 28 comes into contact with a conical wall surface 21 formed by the valve seat 20; and the sealing ring 26 is pressed against the conical wall surface of the valve seat 20.
In a state in which male and female coupling members making up the pipe coupling are connected to each other, the valve body 12 is retracted against the coil spring and separated from the valve seat 20 so that the fluid passage 16 is opened.
When the male and female coupling members are disconnected, the valve body 12 is displaced by the coil spring 36 toward the closed position. However a problem exists with this configuration in that an urging force applied by the coil spring 36 to the valve body 12 may not be uniform. And moreover, effects due to the fluid flowing around the periphery, so as shown in FIG. 2, the valve body 12 may approach the valve seat 20 in a state slightly inclined with respect to the centerline of the fluid passage 16.
In this case, the side surface of the valve head 28 may come into contact with the conical wall surface 21 before the conical part 30 of the valve head 28 makes proper contact with the conical wall surface 21. However, the conical part 30 of the valve head 28 and the sealing ring 26 have the positional relationship illustrated in FIG. 3. Namely, within the plane containing the centerline of the fluid passage 16, the angle β that the line tangent to the conical part 30 and the sealing ring 26 makes with respect to the centerline is greater than the angle α that the conical wall surface 21 of the valve seat 20 makes with respect to the centerline. Thus, in the situation described above in the event that the valve body 12 is slightly inclined when approaching the valve seat 20, the sealing ring 26 will come into contact with the conical wall surface 21 of the valve seat 20, and friction generated between the sealing ring 26 and the conical wall surface 21 of the valve seat 20 will prevent the valve body 12 from advancing completely to the fluid passage closed position. Accordingly, a risk exists of incomplete closure of the fluid passage 16.
In order to solve the problem stated above, a pipe coupling has been developed wherein a cylindrical step is provided in an intermediate portion of the conical wall surface of the valve head, and the end opening of the fluid passage has a predetermined length in the axial direction, so that the cylindrical step enters the end opening before the sealing ring engages the conical wall surface, thus correcting any inclination in the valve body so that the valve body properly reaches the fluid passage closed position (e.g., the publication of examined Japanese utility model application number JP-Y-S50-31964).
In contrast, a pipe coupling has also been developed wherein, assuming that an inclination of the valve body cannot be adequately corrected with only engagement between a cylindrical step of a valve head and an end opening, a plate-shaped guide protruding forward is provided at the center of the tip of the valve head, so that the guide continuously slides within the end opening to correct any inclination of the valve body (e.g., JP-Y-S62-31748).